The present invention relates generally to playground apparatus, and specifically to a type of swing that allows either a single or two occupants to rotate 360.degree. about a horizontal axis while remaining in an upright position.
Conventional playground swings are constructed to allow the occupant of the swing to move in a path below the axis of rotation in an arcuate path. Complete rotation about the axis of rotation for a conventional swing is impossible since the means of connecting the seat on which the occupant rests is normally flexible. Furthermore, even if enough propulsion could be provided to the occupant and the connecting means were right, the occupant would be in an inverted position at one portion of the rotation. In addition, the potential energy of the occupant is such a swing would be large enough to create a dangerously high speed of rotation if the potential energy of the occupant's position above the axis of rotation would be converted into kinetic energy by continued rotation.
Several references teach playground apparatus utilizing rigid frames that rotate 360.degree. about a horizontal axis. Such structures normally have several bench-type seats mounted on a rigid rotating frame. One such teaching is U.S. Pat. No. 2,789,820, Walker. The Walker patent discloses a playground apparatus similar to a miniature ferris wheel where four-bench-type seats are pivotally mounted on a structure that rotates about a horizontal axis. The occupants propel this device by grasping a circular bar attached to the frame supporting the rotating structure. The circular bar is placed within convenient reach of an occupant of the seats which being pivotally mounted on the rotating structure remain upright throughout the 360.degree. rotation. This apparatus necessarily requires at least two equally weighted occupants so the rotating structure is at least approximately balanced. A single occupant of the Walker device could not propel it by grasping the circular frame. A futher disadvantage of such a device is that a mismatch in the weights of the occupants would make propulsion of the device by the occupants physically demanding. A mismatch in weight distribution may also produce unsafe high speed rotation if the heavier portion of the occupant-laden structure is elevated to the uppermost position and allowed to rotate without restraint.
A further disadvantage of such a device is the necessity for more than one occupant. The probability of finding four children of similar weight that all want to participate in the same activity, at the same time, for the same amount of time is small. Furthermore, the probability that four children would agree on the relative positioning of the four different occupants makes it more probable that such a device would generate more discord than amusement.
U.S. Pat. No. 3,298,685, Williams, alleviates some of the shortcomings in the prior art by providing a device where a single occupant is rotated on a frame 360.degree. about a horizontal axis of rotation counterbalanced by a weight. In this reference, a bench-type seat is pivotally mounted on one extremity of a rotating frame and the occupant of the seat propels the device by changing his center of gravity relative to the axis of rotation. A weight is mounted on the end of the rotating frame opposite the occupant. The weight is adjusted by moving the weight on a threaded shaft in relation to the axis of rotation of the rotating frame. By manipulating the position of the weight on the shaft, the occupant can counterbalance his weight to allow rotation of the device without a large gain in momentum upon rotation. This type of device is limited in appeal because of the relatively indirect method of propelling the rotating device. In contrast to the present invention, the Williams patent teaches the immobilizing of the occupants'legs while the present invention relies on the occupant propelling the device by pushing off the ground with the legs. The use of the legs for propulsion provides a more direct form of propulsion, a more exciting ride and more healthy exercise than any of the prior art devices.